Aerodynamic performance of high-speed train under heavy rain condition

In order to study the influence of heavy rain on the aerodynamic performance of a high-speed train, the aerodynamics computation model of high-speed train under heavy rain was established based on the Euler-Lagrange method. The air was modelled as the continuous phase, which was described by the Euler method. The raindrop was modelled as the discrete phase, which was described by the Lagrange method. The two-way coupled method was used to simulate the rainfall environment. The calculation of train aerodynamic performance and raindrop simulation were carried out, respectively, and the accuracy of the calculation method was verified by comparing with the experimental data. The flow field structure and aerodynamic performance of a high-speed train under heavy rain conditions were simulated numerically. Calculation result shows that with the increasing of rainfall intensity, under the impact of raindrops, the positive pressure on the front-end area of streamlined head increases, and the negative pressure on the back-end area of streamlined head decreases. As a result, the aerodynamic drag of head car increases. The rainfall intensity has great influence on the aerodynamic drag coefficient of the head car of a train, while has little influence on the aerodynamic lift coefficient. Compared with the aerodynamic drag coefficient under no rain conditions, when the rainfall intensity is 100-500 mm·h^-1, for the train speed of 200 km·h^-1, the aerodynamic drag coefficient increases by 0.004 0-0.020 4, the aerodynamic drag increases by 85-432 N, and the increasing percentage is 2.64%-13.46%. For the train speed of 300 km·h^-1, the aerodynamic drag coefficient increases by 0.002 7-0.013 7, the aerodynamic drag increases by 129-652 N, and the increasing percentage is 1.78%-9.05%. For the train speed of 400 km·h^-1, the aerodynamic drag coefficient increases by 0.002 3-0.009 8, the aerodynamic drag increases by 195-829 N, and the increasing percentage is 1.52%-6.49%. Therefore, the aerodynamic drag coefficient increases with the rainfall intensity at different train speeds, and there is an approximately linear relationship between the coefficient and the rainfall intensity. Under the train speed of 300 km·h^-1 and the raindrop intensity of 100 mm·h^-1, when the raindrop diameter increases from 2 mm to 4 mm, the aerodynamic drag coefficient increases from 0.152 0 to 0.154 9, the aerodynamic drag increases by 138 N, and the increasing percentage is 1.91 %. Therefore the aerodynamic drag coefficient of a high-speed train increases with the increasing of raindrop diameter, and there is an approximately linear relationship between the coefficient and the raindrop diameter.